The prior art embraces capping units such as will apply caps automatically to respective containers, consisting generally in a plurality of capping assemblies set in motion on a carousel rotatable about a vertical axis.
By way of example, European Patent EP 0636573 owned by the present applicant discloses a unit in which each capping assembly is set in rotation, about a respective axis parallel to the axis of rotation of the carousel, by a respective shaft capable of axial movement relative to the carousel in such a way that the assembly can be shifted toward and away from a relative container revolving on the carousel.
Each capping assembly is equipped with a relative mechanism such as a gripper, by means of which the cap is clasped and screwed onto the threaded neck of a respective container by inducing a rotation of the aforementioned shaft.
The carousel consists substantially in a frame carrying a vertical main drum and a platform at the top of the drum. The frame also serves to support the containers, each aligned beneath a respective capping assembly.
The shafts of the single capping assemblies are carried by a housing associated with the top platform and equipped internally with a stationary drum cam surmounting the main drum of the carousel.
The drum cam presents a side wall affording annular groove cam profiles, such as will accommodate following rollers connected to the shafts of the single capping assemblies and able thus to bring about their vertical movement, also a ring gear integral with the outer surface presented by the side wall of the drum cam. Each of the shafts supporting a capping assembly carries a pinion in mesh with the ring gear of the drum cam.
Thus, when the drum is set in motion around the axis of rotation, the interaction of each pinion with the fixed ring gear of the drum cam will cause the capping assembly to rotate about its own axis. The vertical and rotational movement transmitted to the shafts of the capping assemblies and the movement of the associated grippers are all synchronized in such a manner that successive caps can be taken up by the grippers and screwed onto the respective containers.
The cap is screwed onto the container applying a predetermined tightening torque beyond which a torque limiting device, for example an adjustable clutch associated with each assembly, will begin to slip and thus allow the grippers to lock and terminate the step of screwing the cap onto the neck.
Capping units of the type outlined above are effective, but affected nonetheless by significant drawbacks.
In reality, whilst the aforementioned capping units are able to effect a secure closure of the cap on the container, the applicant finds that there are certain shortcomings as regards the versatility of such units, in terms of the extent to which they can be used with containers of different sizes.
More exactly, it will be appreciated that the vertical travel of each capping assembly depends on the profile of the groove afforded by the drum cam, which positions each capping assembly at a given height, enabling the gripper to engage the cap.
This means that if containers of different height are fed onto the carousel, the drum cam cannot be used as it will no longer be possible to position the gripper at the height of the new container. Generally speaking, the capping unit will utilize a carousel adapted to the size of a given container, with a cam profile allowing the gripper to be positioned at the correct height.
Consequently, the production line must be equipped with a number of units, each dedicated to a certain size of container, generating an increase in costs and a requirement for additional space in which to accommodate the various distinct units.
Another drawback stems from the construction costs and the overall dimensions of the single dedicated capping units.
This drawback is attributable to the use of mechanical components by which each of the individual capping assemblies is set in rotation; besides being bulky and cumbersome, the components in question are particularly costly and require frequent maintenance.
In effect, the mechanical components in question are precision-engineered parts calling for particular care in assembly, in order to ensure that each cap will be closed accurately on the container. A case in point is the adjustable clutch, for example, which not only must be set up for each production run according to the type of container and cap, but is also made to extremely high specifications and thus notably expensive.
The object of the present invention is to overcome the problems associated with the prior art by providing a capping unit for closing containers with respective caps, such as will be versatile and suitable for use with any type of container, irrespective of size.
In particular, one important object of the present invention is to set forth a capping unit such as will be adaptable easily to any type of container used in production, regardless of the dimensions.
A further object of the present invention is to provide a particularly economic and compact capping unit, though without losing the functional advantages typical of the prior art.